Cover member, light scanning apparatus, and image forming apparatus

ABSTRACT

A cover member to be attached to a housing including a bottom portion and a side wall, the cover member including: a closing surface configured to close an opening surrounded by the side wall; at least three protruding portions protruding from the closing surface so as to be located on an inside of the housing; and a protection portion configured to protect a circuit board fixed to the side wall, the protection portion having: a first opposed portion opposed to the circuit board and provided to stand on the closing surface; a second opposed portion opposed to the circuit board and protruding with respect to the first opposed portion away from the circuit board; and a connecting portion configured to connect the first opposed portion and the second opposed portion, wherein a length of the at least three protruding portions is larger than a length of the first opposed portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cover member of a light scanningapparatus to be used in an image forming apparatus.

2. Description of the Related Art

As an electrophotographic image forming apparatus, a copying machine, aprinter, a facsimile, and a multi-function device of those machines areexemplified. As a light scanning apparatus to be used in an imageforming apparatus, a light scanning apparatus having the followingconfiguration has been known. That is, the light scanning apparatusforms an electrostatic latent image on a photosensitive member in such amanner that a rotary polygon mirror deflects a light beam emitted from alight source, and an optical component such as a lens and a mirrorguides the deflected light beam onto a photosensitive surface of thephotosensitive member.

An overview of components of a generally adopted related-art lightscanning apparatus will be described below. A semiconductor laser deviceis provided in a light source portion, and a circuit board connected tothe light source portion is arranged on an outer side of a side wall ofa housing. The circuit board is fixed on the housing with a screw, aspring member, or an adhesive. On the circuit board, a variable volumeis fixed. The variable volume adjusts a light intensity of a light beamemitted from the light source portion to a light intensity correspondingto characteristics of the image forming apparatus. The variable volumeis adjusted when initializing the apparatus at the time of assembly ofthe apparatus in a factory. The variable volume is adjusted to a defaultvalue, and thus a default light intensity of the light beamcorresponding to the characteristics of the image forming apparatus isdetermined. With reference to the default light intensity, the lightintensity of the light beam at the time of image formation iscontrolled.

At the time of assembly of the light scanning apparatus, at the time oftransportation of the light scanning apparatus, and at the time ofoperation of mounting the light scanning apparatus into the imageforming apparatus, a hand and cloth of an operator, a packing materialfor transportation, or a component provided at a periphery of the lightscanning apparatus may be sometimes brought into contact with a controlcircuit board. In this case, setting of the variable volume provided onthe circuit board is fluctuated, and thus the default value may bedeviated. As a result, such image failure occurs that density of anoutput image is light or dark. Adjustment by the variable volume needs adedicated jig capable of high-precision measurement. In a case where thevariable volume is deviated from the default value after the lightscanning apparatus is mounted in the image forming apparatus, thefollowing problem arises. Normally, the light scanning apparatus isassembled in a clean room in which a dust amount in the air iscontrolled or in an environment approximate to the clean room. In a casewhere the variable volume is changed, in order to correct the defaultlight intensity of the light beam, after cleaning the light scanningapparatus, the light scanning apparatus needs to be brought again intoan assembly line for the light scanning apparatus so that the assemblyoperation of the apparatus may consume a lot of time.

To address the above-mentioned problem, in Japanese Patent ApplicationLaid-Open No. 2009-265503, there is proposed a configuration in which,in addition to a main cover configured to protect an inside of the lightscanning apparatus from contamination, a protection member configured tocover the circuit board is provided. Further, there is also proposed aconfiguration in which a projecting portion is formed on a part of themain cover and the projecting portion covers the circuit board.

However, in the configuration disclosed in Japanese Patent ApplicationLaid-Open No. 2009-265503 in which the protection member is provided, astep of mounting a member configured to cover the circuit board isrequired in assembling steps, and hence the operation may becomplicated. Meanwhile, in the configuration in which the projectingportion is formed on the part of the main cover, complicated operationis not caused, but the following problem arises. That is, the projectingportion formed on the cover member disables stable stacking of aplurality of cover members, and hence efficiency of conveying the covermembers in a factory is reduced.

SUMMARY OF THE INVENTION

The present invention has been made under such circumstances, andprovides a cover member, a light scanning apparatus, and an imageforming apparatus which improve transport efficiency while preventingdeformation and breakage of the cover member.

In order to solve the above-mentioned problems, the present inventionhas the following configurations.

According to an embodiment of the present invention, there is provided acover member to be attached to a housing including a bottom portion onwhich a rotary polygon mirror is mounted and a side wall provided tostand on the bottom portion, the cover member comprising: a closingsurface configured to close an opening surrounded by the side wall, therotary polygon mirror being passed through the opening when the rotarypolygon mirror is to be mounted on the bottom portion; at least threeprotruding portions protruding from the closing surface so as to belocated on an inside of the housing in a state in which the cover memberis attached to the housing; and a protection portion configured toprotect a circuit board fixed to the side wall of the housing, theprotection portion having: a first opposed portion opposed to thecircuit board and provided to stand on the closing surface; a secondopposed portion opposed to the circuit board and protruding with respectto the first opposed portion away from the circuit board; and aconnecting portion configured to connect the first opposed portion andthe second opposed portion, wherein a length S of the at least threeprotruding portions from the closing surface in a directionperpendicular to the closing surface and a length T of the first opposedportion in the direction perpendicular to the closing surface satisfy arelation of S>T.

According to an embodiment of the present invention, there is provided alight scanning apparatus, comprising: a light source configured to emita light beam; a rotary polygon mirror configured to deflect the lightbeam to cause the light beam emitted from the light source to scan aphotosensitive member in a scanning direction; an optical memberconfigured to guide the light beam deflected by the rotary polygonmirror to the photosensitive member; a housing configured to contain thelight source, the rotary polygon mirror, and the optical member; and thecover member described above.

According to an embodiment of the present invention, there is providedan image forming apparatus, including: a photosensitive member; thelight scanning apparatus described above, which irradiates a light beamonto the photosensitive member to form an electrostatic latent image; adeveloping unit configured to develop the electrostatic latent imageformed by the light scanning apparatus, to thereby form a toner image;and a transfer unit configured to transfer the toner image formed by thedeveloping unit onto a recording medium.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an overview of an image formingapparatus according to first to forth embodiments.

FIG. 2A is a perspective view of a light scanning apparatus according tothe first embodiment.

FIG. 2B is a cross-sectional view of the light scanning apparatusaccording to the first embodiment.

FIG. 2C is a perspective view of a cover member and a housing of thelight scanning apparatus according to the first embodiment.

FIG. 2D is an enlarged view of a framed rectangle area IID in FIG. 2C.

FIG. 2E is a perspective view of the light scanning apparatus accordingto the first embodiment in which the cover member is mounted on thehousing.

FIG. 3A is a cross-sectional view of a plurality of stacked covermembers according to the first embodiment.

FIG. 3B is an enlarged cross-sectional view of a framed rectangle areaIIIB in FIG. 3A.

FIG. 3C is an enlarged cross-sectional view of a framed rectangle areaIIIC in FIG. 3A.

FIG. 4A is a perspective view of a light scanning apparatus according tothe second embodiment.

FIG. 4B is a diagram of the light scanning apparatus according to thesecond embodiment viewed from a side of a control circuit board.

FIG. 5 is a diagram illustrating a configuration of a cover memberaccording to the third embodiment.

FIG. 6 is a diagram illustrating a configuration of the light scanningapparatus.

FIG. 7A and FIG. 7B are perspective views of a cover member according toa fourth embodiment.

FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D illustrate the cover member to beattached to a housing.

FIG. 9A is a perspective view illustrating a backside of the covermember illustrated in FIG. 7A.

FIG. 9B is a diagram of the cover member looking from a lateral view.

FIG. 10A and FIG. 10B are perspective views of a plurality of stackedcover members.

DESCRIPTION OF THE EMBODIMENTS

Now, modes for carrying out the present invention will be described indetail according to embodiments with reference to the drawings.

Configuration of General Light Scanning Apparatus

FIG. 6 illustrates an overview of components of a light scanningapparatus. The light scanning apparatus includes a semiconductor laser(hereinafter referred to as a light source portion) 71 configured toemit laser light (hereinafter referred to as a light beam), and apolygon mirror (hereinafter referred to as a rotary polygon mirror) 42configured to deflect the light beam so as to cause the light beam toscan a photosensitive drum (photosensitive member). Further, the lightscanning apparatus includes a polygon motor unit 41 configured to rotatethe rotary polygon mirror 42, and optical members. As the opticalmembers, the light scanning apparatus includes a collimator lens 43 anda cylindrical lens 44 which shape the light beam entering the rotarypolygon mirror 42. Further, as the optical members, the light scanningapparatus includes at least one fθ lens (hereinafter referred to as anoptical lens) 60 configured to convert the light beam deflected by therotary polygon mirror 42 into scanning light which scans thephotosensitive drum at uniform velocity. In addition, the light scanningapparatus includes a reflection mirror 62 configured to guide the lightbeam deflected by the rotary polygon mirror 42 onto the photosensitivedrum. The light source portion 71 is fixed to a holding memberconfigured to hold the light source portion 71, and the holding memberis fixed to a side wall of a housing of the light scanning apparatus.The light scanning apparatus is configured to allow the light beam toenter an inside of the light scanning apparatus from a hole portionformed in the housing, and a control circuit board is similarly fixed tothe housing with a screw or an elastic member. A variable volume isprovided on the control circuit board. In order to output a desiredvalue corresponding to the photosensitive drum and a developingapparatus of the image forming apparatus at a spot imaging position, alight intensity of the light beam emitted from the light source portion71 is adjusted by the variable volume described below.

Special lens effective surfaces, typified by an aspheric surface, haveincreasingly been adopted as the optical lens 60 with a view toimproving scanning performance. A highly reflective mirror hasincreasingly been adopted as the reflection mirror 62 in order to reducea light intensity loss along with increase in speed of the apparatus.The polygon motor unit 41 often adopts a configuration in which a rotarypolygon mirror having a plurality of reflecting surfaces on an outercircumference of the rotary polygon mirror is rotated at high speed todeflect an incident light beam in a desired direction at high speed. Thelight intensity of the light beam scanned on a surface to be scanned isclosely related to image density. Unintentional fluctuation in lightintensity of the light beam causes a phenomenon that image density of animage formed on a recording sheet being a recording medium is light ordark. Therefore, as described above, there is proposed a light scanningapparatus including a cover member that includes a projecting portionconfigured to protect the control circuit board in order not tofluctuate the adjusted variable volume of the control circuit board.However, the related-art cover member including the projecting portionhas a problem in that it is impossible to increase transportationefficiency while preventing deformation and breakage of the covermember.

Note that, in the following description, a rotation axis direction ofthe rotary polygon mirror of the polygon motor unit 41 is referred to asa Z-axis direction. A main scanning direction being a scanning directionof the light beam, or a longitudinal direction of the optical lens 60and the reflection mirror 62 is referred to as a Y-axis direction. Adirection perpendicular to the Y-axis and the Z-axis is referred to asan X-axis direction.

First Embodiment Image Forming Apparatus

A configuration of an image forming apparatus according to a firstembodiment of the present invention will be described. FIG. 1 is aschematic configuration diagram illustrating an entire configuration ofa tandem-type color laser beam printer according to the embodiment. Thelaser beam printer (hereinafter simply referred to as a printer)includes four image forming engines (image forming portions) 10Y, 10M,10C, and 10Bk (indicated by the dashed lines) each configured to form atoner image of yellow (Y), magenta (M), cyan (C), or black (Bk).Further, the printer includes an intermediate transfer belt 20 ontowhich the toner image is transferred from each of the image formingengines 10Y, 10M, 10C, and 10Bk. The printer transfers the toner imagetransferred in multiple layers on the intermediate transfer belt 20 ontoa recording sheet P being a recording medium, and thus forms a fullcolor image. In the following description, symbols Y, M, C, and Bkrepresenting respective colors are omitted unless otherwise necessary.

The intermediate transfer belt 20 is formed into an endless belt, and ispassed over a pair of belt conveyance rollers 21 and 22. While theintermediate transfer belt 20 is rotated and moved in the directionindicated by the arrow B, the toner image formed by the image formingengine 10 of each color is transferred onto the intermediate transferbelt 20. Further, a secondary transfer roller 65 is arranged at aposition opposite to the belt conveyance roller 21 across theintermediate transfer belt 20. The recording sheet P is passed betweenthe secondary transfer roller (transfer unit) 65 and the intermediatetransfer belt 20 in pressure contact with each other, and the tonerimage is transferred on the recording sheet P from the intermediatetransfer belt 20. The above-mentioned four image forming engines 10Y,10M, 10C, and 10Bk are arranged in parallel below the intermediatetransfer belt 20. Onto the intermediate transfer belt 20, each of theimage forming engines 10Y, 10M, 10C, and 10Bk transfers the toner imageformed in accordance with image information of a corresponding color(hereinafter this operation is referred to as primary transfer). Thefour image forming engines 10 are arranged along a rotation direction(indicated by the arrow B) of the intermediate transfer belt 20 in thefollowing order: the image forming engine 10Y for yellow; the imageforming engine 10M for magenta; the image forming engine 10C for cyan;and the image forming engine 10Bk for black.

Further, a light scanning apparatus 40 is arranged below the imageforming engines 10. In accordance with the image information, the lightscanning apparatus 40 exposes with light a photosensitive drum 50serving as a photosensitive member provided to each of the image formingengines 10. The light scanning apparatus 40 is shared by all of theimage forming engines 10Y, 10M, 10C, and 10Bk, and includes four lightsource portions (not shown) each configured to emit the light beammodulated in accordance with the image information of each color.Further, the light scanning apparatus 40 includes the rotary polygonmirror 42 configured to deflect the light beam so as to cause the lightbeam corresponding to each photosensitive drum 50 to scan thephotosensitive drum 50 along a rotation axis direction (Y-axisdirection) of the photosensitive drum 50, and the polygon motor unit 41configured to rotate the rotary polygon mirror 42. By the opticalmembers mounted on the light scanning apparatus 40, the light beamdeflected by the rotary polygon mirror 42 is guided onto thephotosensitive drum 50 (onto the photosensitive member), to therebyexpose the photosensitive drum 50 with light.

Each image forming engine 10 includes the photosensitive drum 50, and acharging roller (charging member) 12 configured to uniformly charge thephotosensitive drum 50 to electric potential of a background portion.Further, each image forming engine 10 includes a developing device(developing unit) 13 configured to develop an electrostatic latentimage, which is formed on the photosensitive drum 50 through exposurewith the light beam, to thereby form the toner image. The developingdevice 13 forms the toner image in accordance with the image informationof each color on the photosensitive drum 50.

At a position opposite to the photosensitive drum of each image formingengine 10, a primary transfer roller (transfer unit) 15 is arrangedacross the intermediate transfer belt 20. A predetermined transfervoltage is applied to the primary transfer roller 15, and thus the tonerimage on the photosensitive drum 50 is transferred onto the intermediatetransfer belt 20.

Meanwhile, the recording sheet P is fed from a feed cassette 2 providedin a lower portion of a printer housing 1 into an inside of the printer,specifically, into a secondary transfer position at which theintermediate transfer belt 20 and the secondary transfer roller 65 arein contact with each other. A pick-up roller 24 configured to draw outthe recording sheet P contained in the feed cassette 2, and a feedroller 25 are arranged in parallel at an upper portion of the feedcassette 2. Further, a retard roller 26 configured to prevent a doublefeed of the recording sheets P is arranged at a position opposite to thefeed roller 25. A conveyance path 27 for the recording sheet P in aninside of the printer is provided substantially vertically along a rightside surface of the printer housing 1. The recording sheet P that isdrawn out from the feed cassette 2 positioned at a bottom portion of theprinter housing 1 is conveyed upward through the conveyance path 27 andfed to registration rollers 29 which control timing of causing therecording sheet P to enter the secondary transfer position. Then, afterthe toner image is transferred on the recording sheet P at the secondarytransfer position, the recording sheet P is fed to a fixing device 3(illustrated by the broken line) provided on a downstream side in aconveyance direction. The recording sheet P on which the toner image isfixed by the fixing device 3 is delivered via delivery rollers 28 onto adelivery tray 1 a provided at an upper portion of the printer housing 1.Note that, irradiation windows 142 serve as transmission windows throughwhich a light beam LY, a light beam LM, a light beam LC, and a lightbeam LBk described below are emitted from a housing 85 to thephotosensitive drums 50.

In accordance with the image information of each color and an electricsignal indicating to what extent the light beam is irradiated on thephotosensitive drum 50, the light scanning apparatus 40 exposes withlight the photosensitive drum 50 of each image forming engine 10 at apredetermined timing and a predetermined light intensity. In this way,the toner image is formed on the photosensitive drum 50 of each imageforming engine 10 in accordance with the image information. In thiscase, in order to attain excellent image quality, a latent image formedby the light scanning apparatus 40 needs to be able to reproduce desiredlatent image potential by the light beam that reproduces a demandedlight intensity. That is, the light scanning apparatus 40 needs toalways produce a stable light intensity with respect to the demandedlight intensity.

Configuration of Light Scanning Apparatus

FIG. 2A is a perspective view of the light scanning apparatus 40according to the embodiment. FIG. 2B is a cross-sectional view of thelight scanning apparatus 40 according to the embodiment. FIG. 2C is aperspective view of a cover member 70 and the housing 85 of the lightscanning apparatus 40 according to the embodiment. FIG. 2D is anenlarged view of a framed rectangle area IID in FIG. 2C. FIG. 2E is aperspective view of the light scanning apparatus 40 according to theembodiment in which the cover member 70 is attached to the housing 85.FIG. 2D illustrates a control circuit board 75 described below. Thelight scanning apparatus 40 according to the embodiment includes thehousing 85 in which various components are mounted, and the cover member70 configured to cover an opening portion of the housing 85.

First, with reference to FIG. 2A, a schematic configuration of the lightscanning apparatus 40 according to the embodiment will be described. Ona side wall of the housing 85 of the light scanning apparatus 40according to the embodiment, a control circuit board 75 a and a lightsource unit 55 a are fixed. The light source unit 55 a includes aholding member (not shown) to which the control circuit board 75 a isfixed. Further, on the side wall of the housing 85 of the light scanningapparatus 40 according to the embodiment, a control circuit board 75 band a light source unit 55 b are fixed. The light source unit 55 bincludes a holding member 73 (refer to FIG. 2D) to which the controlcircuit board 75 b is fixed. A light source portion (not shown)configured to expose the photosensitive drum 50Y with light and a lightsource portion (not shown) configured to expose the photosensitive drum50M with light are fixed to the light source unit 55 a. Further, a lightsource portion (not shown) configured to expose the photosensitive drum50C with light and a light source portion (not shown) configured toexpose the photosensitive drum 50Bk with light are fixed to the lightsource unit 55 b.

A plurality of openings are formed in the side wall of the housing 85,and the light source unit 55 a and the light source unit 55 b are fixedto the plurality of openings, respectively. The light beams emitted fromthe light source unit 55 a and the light source unit 55 b are emitted toan inside of the housing 85 to pass through the plurality of openings(irradiation windows 142).

The rotary polygon mirror 42, the polygon motor unit 41 configured torotate the rotary polygon mirror 42, and a deflecting unit including acircuit board 143 configured to drive the polygon motor unit 41 arefixed to a center portion of the inside of the housing 85. The lightbeams emitted from the light source unit 55 a are deflected by therotary polygon mirror 42 in a +X direction. Further, the light beamsemitted from the light source unit 55 b are deflected by the rotarypolygon mirror 42 in a −X direction.

Optical lenses 60 a to 60 d and reflection mirrors 62 a to 62 hdescribed below are fixed to the inside of the housing 85.

Next, with reference to FIG. 2B, optical paths of the light beams LBk,LC, LM, and LY will be described. The light beam LY, which is emittedfrom the light source unit to correspond to the photosensitive drum 50Y,is deflected by the rotary polygon mirror 42 and enters the optical lens60 a. The light beam LY passes through the optical lens 60 a, and entersthe optical lens 60 b. After passing through the optical lens 60 b, thelight beam LY is reflected by the reflection mirror 62 a. The light beamLY reflected by the reflection mirror 62 a passes through theirradiation window (transparent window) 142 (FIG. 2E), and scans thephotosensitive drum 50Y.

The light beam LM, which is emitted from the light source unit 55 tocorrespond to the photosensitive drum 50M, is deflected by the rotarypolygon mirror 42 and enters the optical lens 60 a. The light beam LMpasses through the optical lens 60 a, and enters the optical lens 60 b.After passing through the optical lens 60 b, the light beam LM isreflected by the reflection mirror 62 b, the reflection mirror 62 c, andthe reflection mirror 62 d. The light beam LM reflected by thereflection mirror 62 d passes through the irradiation window(transparent window) 142 (FIG. 2E), and scans the photosensitive drum50M.

The light beam LC, which is emitted from the light source unit 55 tocorrespond to the photosensitive drum 50C, is deflected by the rotarypolygon mirror 42, and enters the optical lens 60 c. The light beam LCpasses through the optical lens 60 c, and enters the optical lens 60 d.The light beam LC passes through the optical lens 60 d, and is reflectedby the reflection mirror 62 e, the reflection mirror 62 f, and thereflection mirror 62 g. The light beam LC reflected by the reflectionmirror 62 g passes through the irradiation window (transparent window)142 (FIG. 2E), and scans the photosensitive drum 50C.

The light beam LBk, which is emitted from the light source unit 55 tocorrespond to the photosensitive drum 50Bk, is deflected by the rotarypolygon mirror 42 and enters the optical lens 60 c. The light beam LBkpasses through the optical lens 60 c, and enters the optical lens 60 d.After passing through the optical lens 60 d, the light beam LBk isreflected by the reflection mirror 62 h. The light beam LBk reflected bythe reflection mirror 62 h passes through the irradiation window(transparent window) 142 (FIG. 2E), and scans the photosensitive drum50Bk.

Configuration of Housing

The housing 85 includes a bottom surface (bottom portion) parallel to anXY plane, and an outer wall (a side wall, hereinafter, also referred toas an outer peripheral portion) provided to stand on the bottom surfacesubstantially in parallel to the Z-axis direction. In contrast to oneend of the outer peripheral portion connected to the bottom surface, theother end of the outer peripheral portion defines an opening(hereinafter also referred to as an opening portion). The rotary polygonmirror 42 and other optical members pass through the opening portion atthe time of assembly of the apparatus, and thus are assembled to thelight scanning apparatus. The housing 85 includes engaging portions 87formed on the housing (hereinafter referred to as housing engagingportions) with which engaging portions 88 formed on the cover member 70(hereinafter referred to as cover engaging portions) described below areengaged. The cover engaging portions 88 and the housing engagingportions 87 form a snap fit mechanism, and the snap fit mechanism fixesthe cover member 70 to the housing 85. A plurality of the light sourceportions 71 are provided, for example, for four colors in a case of afour-color image forming apparatus. Each light source portion 71 isfixed to the outer peripheral portion of the housing 85 in a state ofbeing held by the holding member 73. The control circuit board 75serving as a substrate is fixed to the outer peripheral portion of thehousing 85. Similarly to the light source portions 71, the controlcircuit board 75 is fixed to the outer peripheral portion of the housing85 with a screw. At this time, contact terminal portions 71 a of thelight source portions 71 are bonded and fixed by soldering to holeportions formed in the control circuit board 75.

Further, various electrical components are mounted on the controlcircuit board 75. As one of the electrical components, variable volumes72 configured to vary a laser emission intensity of the light sourceportion 71 are disposed. Two variable volumes 72 are provided for eachlight source. One of the variable volumes 72 has a large resolution inadjusting the light intensity and is used in rough adjustment, andanother of the variable volumes 72 has a small resolution in adjustingthe light intensity and is used in fine adjustment.

Configuration of Cover Member

In order to prevent contamination of the optical components provided inthe inside of the housing 85, the cover member 70 is fixed to thehousing 85 so as to cover the opening portion of the housing 85. Thecover member 70 according to the embodiment includes a first surface 70f (closing surface) configured to cover the opening portion. The firstsurface 70 f is provided with the cover engaging portions 88 to beengaged with the housing engaging portions 87, and a protection portion70 a (portion encircled by the broken line) configured to protect thecontrol circuit board 75 of the light source unit 55 fixed to the sidewall of the housing 85. Further, the first surface 70 f is provided withprotruding portions 77 protruding inside a contour of the first surface70 f of the housing 85 toward the inside of the housing 85 from asurface of the first surface 70 f facing the inside of the housing.Further, the cover member 70 includes the four irradiation windows 142through which the light beam LY, the light beam LM, the light beam LC,and the light beam LBk are emitted. In addition, the cover member 70includes protruding-portion receiving portions (hereinafter simplyreferred to as receiving portions) 77 a. Note that, a surface oppositeto the surface of the cover member 70 facing the housing 85, i.e., anouter surface of the cover member 70 is referred to as a cover-memberbase surface (hereinafter simply referred to as a base surface) 70 e.The receiving portions 77 a are formed on the backside of the surface ofthe cover member 70 on which the protruding portions 77 are formed, andreceive the protruding portions 77 formed on another cover member 70having the same shape.

The cover engaging portions 88 are formed at positions having noprotection portion 70 a in an outer portion of the cover member 70, andprovided to stand on the first surface 70 f of the cover member 70. Whenthe cover member 70 is attached to the housing 85, the cover engagingportions 88 are moved along outer surfaces of the outer peripheralportion of the housing 85, and are engaged with the housing engagingportions 87 formed on the housing 85. The housing engaging portions 87and the cover engaging portions 88 are engaged with each other, and thusthe cover member 70 is fixed to the housing 85.

The protruding portions 77 are formed on the surface of the firstsurface 70 f of the cover member 70 facing the inside of the housing 85so as not to be in contact with various components disposed in thehousing, and not to interfere the optical paths of the light beamstravelling in the housing 85. The protection portion 70 a includes asecond surface 70 b (first opposed portion) and a third surface 70 c(second opposed portion) that cover a surface of each control circuitboard 75 fixed to the side wall of the housing 85. The control circuitboard 75 is covered by the second surface 70 b and the third surface 70c of the protection portion 70 a, and hence fluctuation in the variablevolume 72 due to contact of a hand and cloth of an operator is notcaused, which can solve a problem in that previously-adjusted value ischanged. Note that, the second surface 70 b and the third surface 70 cdo not need to cover an entire part of the control circuit board 75, andonly needs to cover at least a part of the control circuit board 75.

The third surface 70 c of the protection portion 70 a protrudes from thesecond surface 70 b away from the control circuit board 75 with respectto the second surface 70 b. That is, a stepped portion 70 h (steppedsurface) serving as a connecting portion is formed between the secondsurface 70 b and the third surface 70 c.

The cover member 70 is put on the housing 85 in a direction indicated bythe arrow F of FIG. 2C, and the cover engaging portions 88 of the covermember 70 and the housing engaging portions 87 of the housing 85 areengaged with each other. Thus, the light scanning apparatus 40 isconstructed as illustrated in FIG. 2E.

State when Transporting Cover Member

FIG. 3A is a cross-sectional view of a plurality of stacked covermembers 70 according to the embodiment, and illustrates a stacked stateof three cover members 70 (corresponding to a cover member 70A, a covermember 70B, and a cover member 70C from the bottom) in the embodiment.FIG. 3B is an enlarged cross-sectional view of a framed rectangle areaIIIB in FIG. 3A, and illustrates a vicinity of the protection portions70 a of the cover members 70. FIG. 3C is an enlarged cross-sectionalview of a framed rectangle area IIIC in FIG. 3A, and illustrates avicinity of one of the protruding portions 77 of the cover member 70.Note that, in FIG. 3A, FIG. 3B, and FIG. 3C, a cross-section of thecover member 70 is illustrated in a hatched pattern.

The plurality of cover members 70 are superposed and stacked in anup-and-down direction (Z-axis direction), and are transported. Further,at the time of assembly of the light scanning apparatus 40, the covermembers 70 in the stacked state are supplied to an assembly operationperformed by an operator.

As illustrated in FIG. 3A, in a case of stacking the cover members 70,the protection portions 70 a of the cover members 70 overlap with eachother. Specifically, for example, in a direction (Y-axis direction)perpendicular to a mounting surface of the control circuit board 75, thesecond surface 70 b of the protection portion 70 a of the cover member70A overlaps with the third surface 70 c of the cover member 70B stackeddirectly on the cover member 70A. The stepped portion 70 h is formedbetween the second surface 70 b and the third surface 70 c. Thus, theplurality of cover members can be stacked on each other, and spacesaving can be realized at the time of transportation of the covermembers 70. Note that, a related-art cover member does not have such apart as illustrated in FIG. 3B that a lower cover member overlaps withan upper cover member, and hence the upper cover member 70 can only bestacked on the base surface 70 e of the lower cover member 70.Accordingly, the number of the cover members 70 to be stacked is limitedwhen stacking the plurality of cover members, and the cover members 70assume an unstable state even if stacked. However, the cover members 70according to the embodiment enable stacking of many cover members in astable state.

Further, regarding the protection portion 70 a of the cover member 70according to the embodiment, a surface 70 c 1 of the third surface 70 cis more distant from the control circuit board 75 than a surface 70 b 1of the second surface 70 b. Accordingly, even when the cover bends orpartially warps due to molding, it is possible to solve a problem inthat a distal end of the protection portion 70 a, i.e., a distal end ofthe surface 70 c 1 of the third surface 70 c hits an electricalcomponent on the control circuit board 75 and thus applies a large forceto the electrical component. Here, the surface 70 b 1 of the secondsurface 70 b is nearer to the control circuit board 75 than the surface70 c 1 of the third surface 70 c. The surface 70 b 1 of the secondsurface 70 b is near to a first bending portion 70 f bending from thebase surface 70 e, and hence can be increased in rigidity. Even when thesame force is applied, the surface 70 b 1 warps to a smaller extent thanthe distal end portion of the protection portion 70 a, and thus it ispossible to prevent contact of the protection portion 70 a with thecontrol circuit board 75.

Configurations of Stacking Protruding Portion and Receiving Portion

The cover members 70 include the stacking protruding portions 77 thatare brought into contact with each other when stacking the plurality ofcover members on each other. That is, in a case where the cover member70B is stacked on another cover member 70A, the stacking protrudingportions 77 of the cover member 70B are brought into contact with thereceiving portions 77 a of the cover member 70A. The stacking protrudingportions 77 extend substantially vertically toward the housing 85 (thatis, downward in the Z-axis direction) from the surface of the covermember 70 opposed to the housing 85. In addition, a length (distance Sdescribed below) of the stacking protruding portions 77 from the basesurface 70 e in the Z-axis direction is longer than a length of thecover engaging portions 88 from the base surface 70 e in the Z-axisdirection. That is, the length of each of the cover engaging portions 88extending from the base surface 70 e in the Z-axis direction is shorterthan the length of each of the stacking protruding portions 77 extendingfrom the base surface 70 e in the Z-axis direction. This can preventbreakage of the cover engaging portions 88 when stacking the pluralityof cover members 70.

Note that, a shape of the stacking protruding portion 77 is notparticularly limited. As illustrated in FIG. 2C, the stacking protrudingportion 77 according to the embodiment has a trapezoid shape when viewedfrom the Y-axis direction, and a length of the stacking protrudingportion 77 in the X-axis direction is decreased downward in the Z-axisdirection. Further, when a trapezoid part of the stacking protrudingportion 77 is referred to as a protruding-portion main portion 77 b, asillustrated in FIG. 3C, a rib portion 77 c is formed for maintainingrigidity of the protruding-portion main portion 77 b, and the ribportion 77 c has a shape tapered toward the housing 85 (tapered shape).Accordingly, the stacking protruding portion 77 has, as an entire shape,a tapered part tapered downward in the Z-axis direction. Further, across-sectional shape of the protruding-portion main portion 77 b andthe rib portion 77 c taken on the plane parallel to an XY plane is asubstantially T-shape. That is, the stacking protruding portion 77 hassuch a shape that the area of the substantially T-shape, whichcorresponds to a cross-section of the tapered part of the stackingprotruding portion 77 taken on the plane parallel to the XY plane, isdecreased downward in the Z-axis direction.

Meanwhile, a distal end portion 77 d (a portion enclosed by an ellipseindicated by the broken line in FIG. 3C) of the stacking protrudingportion 77 is brought into contact with the receiving portion 77 a ofthe lower cover member 70, and the distal end portion 77 d does not havea tapered shape. That is, the area of the substantially T-shape in thedistal end portion 77 d of the stacking protruding portion 77 ismaintained constant downward in the Z-axis direction. With thisconfiguration, in a case of stacking one cover member 70 on anothercover member 70, for example, in a case of stacking the cover member 70Bon the cover member 70A, the stacking protruding portion 77 of the covermember 70B does not climb over the receiving portion 70 a of the covermember 70A. This prevents deterioration of stability when stacking thecover members 70.

The receiving portion 77 a of the cover member 70 is formed on the basesurface 70 e of the cover member 70 at a position at which the stackingprotruding portion 77 of the cover member 70 to be stacked above isbrought into contact with the receiving portion 77 a. As illustrated inFIG. 2E, a frame 77 ab is formed to surround the receiving portion 77 aof the cover member 70. The frame 77 ab is formed in such a manner thatonly edge portions of the receiving portion 77 a are ridged so as tosurround a range wider than a range within a shape of the bottom surfaceof the stacking protruding portion 77 is put in. The distal end portion77 d of the stacking protruding portion 77 of the cover member 70Bstacked on the cover member 70A is caught by the frame 77 ab of thereceiving portion 77 a of the cover member 70A, and thus the covermember 70B does not slip over the base surface 70 e of the cover member70A. Note that, as described above, the shape of the stacking protrudingportion 77 is not limited to the above-mentioned configuration, and anyshape may be adopted as long as it satisfies a relation in lengthdescribed below.

At least three stacking protruding portions 77 are provided for eachcover member 70, and the stacking protruding portions 77 are formed soas to stabilize the cover members 70 in a case of stacking the covermembers 70. Note that, four stacking protruding portions 77 are formedin the embodiment. The stacking protruding portions 77 are formed so asnot to be brought into contact with various components in the housing85, and not to interfere the optical paths of the light beam when thecover member 70 is attached to the housing 85.

Relation Among First Surface, Second Surface, and Stacking ProtrudingPortion

When stacking the cover members 70, in a stacking direction (directionindicated by the arrow Z1 in FIG. 3A (Z-axis direction)), the surface 70b 1 of the second surface 70 b, the surface 70 c 1 of the third surface70 c, and the stacking protruding portion 77 are constructed so as tosatisfy the following relation. Note that, reference symbols S, T, and Rdescribed below are illustrated in FIG. 3B and FIG. 3C.

S>T≧R.

S: a distance from the base surface 70 e to the distal end of thestacking protruding portion 77 in the direction indicated by the arrowZ1T: a distance from the base surface 70 e to the distal end of thesurface 70 b 1 of the second surface 70 b in the direction indicated bythe arrow Z1R: a distance from a second bending portion 70 g to the distal end ofthe surface 70 c 1 of the third surface 70 c in the direction indicatedby the arrow Z1

Here, the distal end of the surface 70 b 1 of the second surface 70 bmay be construed as the second bending portion 70 g serving as theconnecting portion. Further, the second bending portion 70 g in thedistance R may be construed as a third bending portion 70 h. Note that,a thickness of the cover member 70 is smaller than the distance S, T, orR.

When the distances S, T, and R satisfy the above-mentioned relation, thefollowing may be said. First, in a case where a relation of S>T issatisfied, even when the cover member 70B is stacked on the cover member70A, the stacking protruding portion 77 of the cover member 70B islonger in length in Z-axis direction than the surface 70 b 1 of thesecond surface 70 b of the protection portion 70 a. Accordingly, thesecond bending portion 70 g of the cover member 70B is not brought intocontact with the base surface 70 e of the cover member 70A. In addition,in a case where a relation of T≧R is satisfied in this state, a lengthof the surface 70 c 1 of the third surface 70 c of the cover member 70Bis equal to or shorter than a length of the surface 70 b 1 of the secondsurface 70 b of the cover member 70A. Accordingly, the distal end of thesurface 70 c 1 of the third surface 70 c of the cover member 70B is notbrought into contact with the third bending portion 70 h of theprotection portion 70 a of the cover member 70A. With thisconfiguration, when stacking the plurality of cover members 70 at thetime of transportation or at a site of assembling the light scanningapparatus 40, it is possible to prevent deformation and breakage causedby contact between the protection portions 70 a. In a height direction(Z-axis direction) when stacking the plurality of cover members 70, anoverlapping amount of the cover members 70 can be increased. This canreduce an entire height when stacking the plurality of cover members 70,and can reduce an occupied space when stacking the plurality of covermembers.

Further, in the embodiment, the cover engaging portions 88, which areformed for fixing the cover member 70 to the housing 85, are set to besmaller in height than the stacking protruding portions 77. The lengthof each of the cover engaging portions 88 in the Z-axis direction isshorter than the length (distance S) of each of the stacking protrudingportions 77, and thus it is possible to solve a problem in that, whenstacking the plurality of cover members, the cover engaging portions 88are brought into contact with the lower cover member 70 and break due tothe contact.

Note that, in the embodiment, a two-tier configuration is adopted as astepped configuration. However, the stepped configuration is formed inthree tiers, four tiers, or the like, that is, at least two or morestepped surfaces are provided away from a board surface of the controlcircuit board 75, and thus the above-mentioned effects can be obtained.In this case, it is desired that all stepped surfaces have the sameheight (T=R in the case of FIGS. 3A to 3C) or a stepped surface disposedin a higher position in a direction indicated by the arrow Z1 has alonger height (T>R in the case of FIGS. 3A to 3C). For example, in acase where the protection portion 70 a of the cover member 70 has nstepped surfaces (n is a positive integer equal to or longer than two),it is only necessary to satisfy the following relation.

S>T1≧T2 . . . ≧Tn

Here, S represents the length of the stacking protruding portion 77 inthe Z-axis direction as described above. T1 represents a length of afirst surface in a direction (Z-axis direction) perpendicular to thesurface of the cover member 70 opposed to the housing 85. The firstsurface refers to a stepped surface that is nearest, in at least twostepped surfaces, to the surface of the cover member 70 opposed to thehousing 85. T2 represents a length of a second surface in the direction(Z-axis direction) perpendicular to the surface of the cover member 70opposed to the housing 85. The second surface refers to a subsequentstepped surface continuous with the first surface. Tn represents alength of an nth surface in the direction (Z-axis direction)perpendicular to the surface of the cover member 70 opposed to thehousing 85. The nth surface refers to a subsequent stepped surfacecontinuous with an (n−1)th surface. As described above, also in a caseof stacking the plurality of cover members 70 each having n steppedsurfaces, when the above-mentioned relation is satisfied, the sameeffects as those described above can be obtained.

As described above, according to the embodiment, it is possible toincrease transport efficiency while preventing deformation and breakageof the cover member.

Second Embodiment

FIG. 4A is a perspective view of a light scanning apparatus according toa second embodiment. FIG. 4B is a diagram of the light scanningapparatus according to the second embodiment viewed from a side of acontrol circuit board. Note that, the same components as those of thefirst embodiment are denoted by the same reference symbols, anddescription thereof is omitted.

In a part of a cover member 70 according to the embodiment, a guideshaped portion 78 is formed. The guide shaped portion 78 prevents aprotection portion 70 a itself from being brought into contact with anelectrical component of a control circuit board 75 when the cover member70 is attached to the housing 85. The guide shaped portion 78 isarranged at a distance X1 from an end portion of the control circuitboard 75 in a direction (X-axis direction) perpendicular to a directionof attaching the cover member 70 (direction indicated by the arrow Z1(Z-axis direction)). The guide shaped portion 78 is formed by providinga surface 70 c 2 (surface parallel to the YZ plane) perpendicular to asurface 70 c 1 of a third surface 70 c. Note that, above the surface 70c 2 in a vertical direction (Z-axis direction), a surface 70 b 2substantially perpendicular to a surface 70 b 1 of a second surface 70 bis provided. As in the case where the surface 70 b 1 of the secondsurface 70 b and the surface 70 c 1 of the third surface 70 c form thestepped structure by a second bending portion 70 g and a third bendingportion 70 h, the surface 70 b 2 and the surface 70 c 2 also form thestepped structure. With this structure, similarly to the firstembodiment, the plurality of cover members 70 can be stacked.

Note that, in a case where the protection portion 70 a is formed byproviding at least three stepped surfaces, a surface perpendicular tothe stepped surface farthest from the board surface of the controlcircuit board 75 is formed as the guide shaped portion 78. From a basesurface 70 e of the cover member 70 toward the guide shaped portion 78,the surface 70 b 2, the surface 70 c 2, . . . are formed as steppedsurfaces. With this configuration, space saving and stability can bemaintained when stacking the plurality of cover members 70.

With this configuration, in a case where the cover member 70 is attachedto the housing 85, before the protection portion 70 a is brought intocontact with the electrical component mounted on the control circuitboard 75, the guide shaped portion 78 and the housing 85 are broughtinto contact with each other. A description will be provided of, forexample, a case of keeping attaching the cover member 70 on the housing85 in a state in which the cover member 70 is displaced in the Y-axisdirection when the cover member 70 is attached to the housing 85. In acase where the cover member 70 includes no guide shaped portion 78, whenthe cover member 70 is moved downward in the Z-axis direction while thecover member 70 is displaced in the Y-axis direction, the distal end ofthe protection portion 70 a is brought into contact with the controlcircuit board 75. However, in a case where the cover member 70 includesthe guide shaped portion 78, even when the cover member 70 is moveddownward in the Z-axis direction while the cover member 70 is displacedin the Y-axis direction, the guide shaped portion 78 is brought intocontact with the housing 85 before the distal end of the protectionportion 70 a is brought into contact with the control circuit board 75.Accordingly, when the cover member 70 is attached to the housing 85, thecover member itself is reliably attached without contact with thecontrol circuit board 75, and thus it is possible to prevent breakage ofthe electrical component caused by contact of the cover member 70 withthe control circuit board 75.

As described above, according to the embodiment, it is possible toincrease transport efficiency while preventing deformation and breakageof the cover member.

Third Embodiment

FIG. 5 is a schematic configuration diagram illustrating a configurationaccording to a third embodiment of the present invention, and aperspective view looking from a side on which a control circuit board 75is fixed to the housing 85. Note that, the same components as those ofthe first embodiment are denoted by the same reference symbols, anddescription thereof is omitted.

In a surface 70 b 1 of a second surface 70 b of a protection portion 70a (encircled by the broken line), at positions allowing access tovariable volumes 72 serving as adjusting members, opening portions(holes) 79 are formed in the surface 70 b 1 of the second surface 70 b.With this configuration, the opening portions 79 are formed at positionscorresponding to the variable volumes 72, and the protection portion 70a, specifically, the surface 70 b 1 of the second surface 70 b and asurface 70 c 1 of a third surface 70 c are present in vicinities of thevariable volumes 72 with a space from the control circuit board 75.Accordingly, in a state in which a cover member 70 is attached to thehousing 85, access to the variable volumes 72 can be made to adjust alight intensity. In addition, contact of a hand and cloth of an operatorwith the variable volumes 72 can be prevented.

Further, the variable volumes 72 and the opening portions 79 areprovided in the surface 70 b 1 of the second surface 70 b. Meanwhile,the surface 70 c 1 of the third surface 70 c protrudes outward comparedwith the surface 70 b 1 of the second surface 70 b, that is, the surface70 c 1 of the third surface 70 c is distant from the control circuitboard 75. Accordingly, unintentional contact with the variable volumes72 can be prevented.

Here, in a case where the protection portion 70 a of the cover member 70has a plurality of steps, it is desired that the opening portions 79 beformed in a surface except a surface farthest from a board surfaceserving as a surface on which the control circuit board 75 is fixed. Inthe case of FIG. 5, the opening portions 79 are formed not in thesurface 70 c 1 of the third surface 70 c but in the surface 70 b 1 ofthe second surface 70 b. This reason is as follows. That is, when theopening portions 79 are formed in the surface farthest from the controlcircuit board 75 among a plurality of stepped surfaces, the openings areformed in positions close to a distal end of the protection portion 70a. When the openings are formed in the positions close to the distal endof the protection portion 70 a, rigidity of the cover member 70 islocally reduced, which may cause deformation of the cover member 70.Accordingly, in a case where a plurality of stepped surfaces areprovided, the opening portions 79 are formed in a stepped surface excepta stepped surface farthest from the board surface of the control circuitboard 75. Note that, the third embodiment may be applied to theconfiguration according to the second embodiment, which has the guideshaped portion 78. A volume adjusting tool for the variable volumes 72normally has a size of approximately 7 mm (millimeters), and hence it isdesired that the opening portions 79 have a size of approximately 7 mmto 10 mm in consideration of workability. This can facilitate adjustingoperation, and can prevent contact of a hand of an operator except forthe adjusting operation.

As described above, in a case where each variable volume 72 is providedat a position on the control circuit board 75 opposed to the secondsurface 70 b (specifically, an opposite surface of the surface 70 b 1),each opening portion 79 is formed at a position on the second surface 70b opposed to the variable volume 72. Note that, in the embodiment, amongfour variable volumes 72 (refer to FIG. 2D) provided on the controlcircuit board 75, three variable volumes 72 are provided at positionsopposed to the second surface 70 b. Accordingly, the embodiment adopts aconfiguration in which three opening portions 79 are formed in thesecond surface 70 b. Note that, in the embodiment, the three openingportions 79 are formed so as to respectively correspond to the threevariable volumes 72 at the positions opposed to the second surface 70 b.However, a configuration having at least one opening portion 79 may beadopted.

Further, as illustrated in FIG. 2D, one of the four variable volumes 72provided on the control circuit board 75 is provided at a position onthe control circuit board 75 opposed to the third surface 70 c. In thiscase, for the above-mentioned reason, priority is placed on preventionof reduction in rigidity of the cover member 70, and hence the openingportion 79 is not formed in the third surface 70 c (refer to FIG. 5).However, in a case where rigidity of the cover member 70 is not reducedeven when the opening portion 79 is formed in the third surface 70 c,the opening portion 79 may be formed in the third surface 70 c. Further,the opening portion 79 may be formed across the second surface 70 b, thethird surface 70 c, and the stepped portion ranging from a secondbending portion 70 g to a third bending portion 70 h.

As described above, according to the embodiment, it is possible toincrease transport efficiency while preventing deformation and breakageof the cover member. In addition, according to the embodiment, it ispossible to finely adjust the light intensity in a state of protecting amounting surface of the control circuit board 75.

Note that, according to the first to third embodiments, the cover member70 is fixed to the housing 85 by the cover engaging portions 88, but thesame effects can be obtained even when the cover member 70 is fixed tothe housing 85 by a fixing method such as screw fixation. Further, thelight scanning apparatus using the cover member described in the firstto third embodiments is not limited to the above-mentioned lightscanning apparatus. The present invention is also applicable to a lightscanning apparatus having a configuration in which the housing has anopening and the opening is covered by the cover member. In addition, thepresent invention is not limited to the image forming apparatusillustrated in FIG. 1, and is applicable to an image forming apparatusincluding the light scanning apparatus using the cover member.

Fourth Embodiment

With reference to FIGS. 7A and 7B to FIGS. 10A and 10B, a fourthembodiment of the present invention will be described. Descriptions ofcomponents each having the same function as in the first to thirdembodiments are omitted.

FIG. 7A and FIG. 7B are perspective views of a cover member 90 of theembodiment. Unlike the cover member 70 of the first to thirdembodiments, the cover member 90 of the embodiment has no protectionportion 70 a and includes protection protruding portions 91 a, 91 b, 91c, and 91 d at four corners of the cover member 90, the protectionprotruding portions 91 a to 91 d each having a length longer than thatof cover engaging portions 88. An opening defined by a side wall of ahousing 85 of the embodiment has a substantially rectangular shape. Forthat reason, as illustrated in FIG. 7A, the cover member 90 configuredto close the opening also has a substantially rectangular shape. Theprotection protruding portions 91 a to 91 d are provided to stand on thefour corners (four vertices of an outer shape of the cover member 90) ofthe cover member 90 having the substantially rectangular shape.

As illustrated in FIG. 8A and FIG. 8B, when the cover member 90 is to bemoved to a housing 85 in order to fix the cover member 90 to the housing85, the protection protruding portions 91 a to 91 d first overlap with(are opposed to) the side wall of the housing 85 before the coverengaging portions 88 overlap with the side wall on the outer side of thehousing 85 (Reference is made to FIG. 8B.). Specifically, the length ofthe protection protruding portions 91 a to 91 d is longer than that ofthe cover engaging portions 88 in a direction perpendicular to theclosing surface of the cover member 90. When the distal end portions 32of the protection protruding portions 91 a to 91 d are caused to movealong the side wall of the housing 85, the protection protrudingportions 91 a to 91 d are configured to serve as guide members defininga relative movement direction between the cover member 90 and thehousing 85. That is, when the distal end portions 32 of the protectionprotruding portions 91 a to 91 d are moved along the side wall of thehousing 85, a gap formed between the protection protruding portions 91 ato 91 d and the housing 85 is 1 mm or less. Therefore, if the covermember 90 is to be moved in a direction parallel to the closing surfaceof the cover member 90, the protection protruding portions 91 a to 91 dare brought into contact with the side wall of the housing 85, with theresult that the relative movement of the cover member 90 and the housing85 in the direction parallel to the closing surface of the cover member90 is restricted (Reference is made to FIG. 8C.).

The protection protruding portions 91 a to 91 d having the length longerthan that of the cover engaging portions 88 prevent, when the covermember 90 is to be attached to the housing 85, the cover engagingportions 88 from abutting against the top of the side wall of thehousing 85 so that the deformation of the cover engaging portions 88 canbe avoided. In addition, the protection protruding portions 91 a to 91restrict the relative movement between the cover member 90 and thehousing 85 in the direction parallel to the closing surface of the covermember 90, thereby being capable of suppressing the deformation of thecover engaging portions 88, which is caused by the contact between thecover engaging portions and the side wall when the cover member 90 is tobe attached to the housing 85.

FIG. 9A is a perspective view illustrating the backside of the covermember 90 illustrated in FIGS. 7A and 7B. FIG. 9B is a diagram of thecover member 90 looking from a lateral view. As illustrated in FIG. 9A,the cover member 90 is provided with stacking protruding portions 92 a,92 b, 92 c, and 92 d. The stacking protruding portions 92 a to 92 d havethe same function of the stacking protruding portions 77 as illustratedin the first to third embodiments. As illustrated in FIG. 9B, the lengthof the stacking protruding portions 92 a to 92 d is longer than that ofthe protection protruding portions 91 a to 91 d (S>T). In this way, dueto the fact that the length of the stacking protruding portions 92 a to92 d is longer than that of the protection protruding portions 91 a to91 d, as illustrated in FIGS. 10A and 10B, a plurality of the covermembers 90 may be stably stacked by the stacking protruding portions 92a to 92 d. In a state as illustrated in FIGS. 10A and 10B, theprotection protruding portions 91 a to 91 d and the cover engagingportions 88 of an upper cover member 90 are not in contact with a lowercover member 90.

As described above, the length of the protection protruding portions 91a to 91 d is made longer than that of the cover engaging portions 88 andthat of the stacking protruding portions 92 a to 92 d, thereby beingcapable of stably stacking the plurality of the cover members 90.

Note that, in the embodiment, the description is made of the covermember 90 including the protection protruding portions 91 a to 91 d.However, the protection protruding portions 91 a to 91 d may notnecessarily be provided on the cove member 90. In this configuration,when the length of the stacking protruding portions 92 a to 92 d islonger than that of the cover engaging portions 88, the plurality of thecover members 90 can be stably stacked without bringing the coverengaging portions 88 of an upper cover member 90 into contact with alower cover member 90.

Further, in the embodiment, there are exemplified four stackingprotruding portions 91 a to 91 d. However, the stacking protrudingportions may be arranged so that the plurality of the cover members maybe stably stacked. Consequently, depending on the shape of the cover andthe arrangement of the stacking protruding portions, at least threestacking protruding portions are required. The same is true in the firstto third embodiments.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-131657, filed Jun. 24, 2013, and Japanese Patent Application No.2014-122592, filed Jun. 13, 2014, which are hereby incorporated byreference herein in their entirety.

What is claimed is:
 1. A cover member to be attached to a housingincluding a bottom portion on which a rotary polygon mirror is mountedand a side wall provided to stand on the bottom portion, the covermember comprising: a closing surface configured to close an openingsurrounded by the side wall, the rotary polygon mirror being passedthrough the opening when the rotary polygon mirror is to be mounted onthe bottom portion; at least three protruding portions protruding fromthe closing surface so as to be located on an inside of the housing in astate in which the cover member is attached to the housing; and aprotection portion configured to protect a circuit board fixed to theside wall of the housing, the protection portion having: a first opposedportion opposed to the circuit board and provided to stand on theclosing surface; a second opposed portion opposed to the circuit boardand protruding with respect to the first opposed portion away from thecircuit board; and a connecting portion configured to connect the firstopposed portion and the second opposed portion, wherein a length S ofthe at least three protruding portions from the closing surface in adirection perpendicular to the closing surface and a length T of thefirst opposed portion in the direction perpendicular to the closingsurface satisfy a relation of S>T.
 2. A cover member according to claim1, further comprising a cover engaging portion provided to stand on theclosing surface along an outer side of the side wall of the housing tobe engaged with a housing engaging portion provided on the outer side ofthe side wall of the housing, wherein the cover member is attached tothe housing by the cover engaging portion being engaged with the housingengaging portion, and wherein a length of the cover engaging portion inthe direction perpendicular to the closing surface is shorter than thelength of the at least three protruding portions in the directionperpendicular to the closing surface.
 3. A cover member according toclaim 1, wherein each of the at least three protruding portions has adistal end portion of which an area in a cross-section parallel to aplane opposed to the housing is maintained constant in the directionperpendicular to the closing surface.
 4. A cover member according toclaim 1, wherein the closing surface is provided with receiving portionsconfigured to receive protruding portions of another cover member havingthe same shape as the cover member, the receiving portions beingprovided on a backside opposed to a surface of the closing surface onwhich the at least three protruding portions are provided.
 5. A covermember according to claim 4, wherein each of the receiving portions hasa ridged frame.
 6. A cover member according to claim 1, wherein, when aplurality of cover members are stacked on top of each other, a coverengaging portion of an upper cover member is out of contact with a lowercover member and the upper cover member is placed on the lower covermember by the at least three protruding portions of the upper covermember.
 7. A light scanning apparatus, comprising: a light sourceconfigured to emit a light beam; a rotary polygon mirror configured todeflect the light beam to cause the light beam emitted from the lightsource to scan a photosensitive member in a scanning direction; anoptical member configured to guide the light beam deflected by therotary polygon mirror to the photosensitive member; a housing configuredto contain the light source, the rotary polygon mirror, and the opticalmember; and a cover member as recited in claim
 1. 8. A light scanningapparatus according to claim 7, wherein the at least three protrudingportions are located without blocking an optical path of the light beamin the housing.
 9. An image forming apparatus, comprising: aphotosensitive member; a light scanning apparatus as recited in claim 7,the light scanning apparatus emitting a light beam to the photosensitivemember to form an electrostatic latent image; a developing unitconfigured to develop the electrostatic latent image formed by the lightscanning apparatus to form a toner image; and a transfer unit configuredto transfer the toner image formed by the developing unit onto arecording medium.
 10. A cover member to be attached to a light scanningapparatus including: a housing having a bottom portion on which a rotarypolygon mirror is mounted and a side wall provided to stand on thebottom portion; and housing engaging portions provided in a plurality ofpositions on an outside of the side wall of the housing, the covermember comprising: a closing surface configured to close an openingsurrounded by the side wall, the rotary polygon mirror being passedthrough the opening when the rotary polygon mirror is to be mounted onthe bottom portion; cover engaging portions paired up with the housingengaging portions, respectively, and provided to stand in a plurality ofpositions on the closing surface of the cover member so that the coverengaging portions are opposed to the side wall provided with the housingengaging portions and engaged with the housing engaging portions pairedup, respectively, in a state in which the cover member is attached tothe housing; and at least three protruding portions protruding from theclosing surface so as to be located on an inside of the housing in astate in which the cover member is attached to the housing, wherein alength of the at least three protruding portions is longer than a lengthof the cover engaging portions in a direction perpendicular to theclosing surface.
 11. A cover member according to claim 10, wherein, whena plurality of cover members are stacked on top of each other, coverengaging portions of an upper cover member are out of contact with alower cover member and the upper cover member is placed on the lowercover member by the at least three protruding portions of the uppercover member.
 12. A cover member according to claim 10, wherein each ofthe at least three protruding portions has a distal end portion of whichan area in a cross-section parallel to a plane opposed to the housing ismaintained constant in the direction perpendicular to the closingsurface.
 13. A cover member according to claim 10, wherein the closingsurface is provided with receiving portions configured to receiveprotruding portions of another cover member having the same shape as thecover member, the receiving portions being provided on a backsideopposed to a surface of the closing surface on which the at least threeprotruding portions are provided.
 14. A cover member according to claim10, wherein each of the receiving portions has a ridged frame.
 15. Acover member according to claim 10, further comprising a plurality ofprotection protruding portions provided to stand on the closing surfaceof the cover member so as to be opposed to the side wall in the state inwhich the cover member is attached to the housing, wherein a length ofthe plurality of the protection protruding portions is longer than thelength of the cover engaging portions, and wherein the length of the atleast three protruding portions is longer than the length of theplurality of the protection protruding portions in the directionperpendicular to the closing surface.
 16. A cover member according toclaim 10, wherein the plurality of the protection protruding portionsand the cover engaging portions are provided to stand on the closingsurface of the cover member so that, when the cover member is to beattached to the housing, a distal end of at least one of the pluralityof the protection protruding portions passes a top of the side wall ofthe housing before distal ends of the cover engaging portions pass thetop of the side wall of the housing.
 17. A light scanning apparatus,comprising: a light source configured to emit a light beam; a rotarypolygon mirror configured to deflect the light beam to cause the lightbeam emitted from the light source to scan a photosensitive member in ascanning direction; an optical member configured to guide the light beamdeflected by the rotary polygon mirror to the photosensitive member; ahousing configured to contain the light source, the rotary polygonmirror, and the optical member; and a cover member as recited in claim10.
 18. A light scanning apparatus according to claim 17, wherein the atleast three protruding portions are located without blocking an opticalpath of the light beam in the housing.
 19. An image forming apparatus,comprising: a photosensitive member; a light scanning apparatus asrecited in claim 17, the light scanning apparatus emitting a light beamto the photosensitive member to form an electrostatic latent image; adeveloping unit configured to develop the electrostatic latent imageformed by the light scanning apparatus to form a toner image; and atransfer unit configured to transfer the toner image formed by thedeveloping unit onto a recording medium.